II. (8) First of all, therefore, the husbandman is not anxious to plant or to sow anything that is unproductive, but only all such things as are worth cultivation, and as bear fruit, which will bring a yearly produce to their master man. For nature has pointed him out as the master of all trees and animals, and all other things whatever which are perishable; (9) and what can man be but the kind that is in every one of us, which is accustomed to reap the advantage from all that is sown or planted? But since milk is the food of infants, but cakes made of wheat are the food of fullgrown men, so also the soul must have a milk-like nourishment in its age of childhood, namely, the elementary instruction of encyclical science. But the perfect food which is fit for men consists of explanations dictated by prudence, and temperance, and every virtue. For these things being sown and implanted in the mind will bring forth most advantageous fruit, namely, good and praiseworthy actions. (10) By means of this husbandry, all the trees of the passions and vices, which soot forth and grow up to a height, bringing forth pernicious fruits, are rooted up, and cut down, and cleared away, so that not even the smallest fragment of them is left, from which any new shoots of evil actions can subsequently spring up. (11) And if, besides, there are any trees which produce no fruit at all, neither good nor bad, the husbandman will cut them down too, but still he will not suffer them to be completely destroyed, but he will apply them to some appropriate use, making them into stakes and fixing them as pales all round his homestead, or using them as a fence for a city to serve instead of a wall.

III. (12) For Moses says, “Every tree which bringeth not forth fruit good to eat thou shalt cut down; and thou shalt make it into stakes against the city which shall make war upon them.”{2} {#De 20:20.} And these trees are likened to those powers developed in words alone, which have nothing in them but mere speculation, (13) among which we must class medical science, when unconnected with practice, by which it is natural that such persons may be cured, and also the oratorical and hireling species of rhetoric, which is conversant not about the discovery of the truth, but solely about the means of deceiving the hearers by plausible persuasion; and in the same class we must place all those parts of dialectics and geometry which have no connection with a proper regulation of the character or morals, but which only sharpen the mind, not suffering it to exercise a dull apprehension towards each question which is raised and submitted to it, but always to dissect the question and divide it, so as to distinguish the peculiar character of each thing from the common qualities of the whole genus. (14) At all events, men say, that the ancients compared the principles of philosophy, as being threefold, to a field; likening natural philosophy to trees and plants, and moral philosophy to fruits, for the sake of which the plants are planted; and logical philosophy to the hedge or fence: (15) for as the wall, which is erected around, is the guardian of the plants and of the fruit which are in the field, keeping off all those who wish to do them injury and to destroy them, in the same manner, the logical part of philosophy is the strongest possible sort of protection to the other two parts, the moral and the natural philosophy; (16) for when it simplifies twofold and ambiguous expressions, and when it solves specious plausibilities entangled in sophisms, and utterly destroys seductive deceits, the greatest allurement and ruin to the soul, by means of its own expressive and clear language, and its unambiguous demonstrations, it makes the whole mind smooth like wax, and ready to receive all the innocent and very praiseworthy impressions of sound natural and moral philosophy.